Land cover concerns the spatial distribution
of physical cover including vegetation types and human uses
of land for living, agriculture and forestry, and commercial
space.

Land
cover affects and is affected by global climate change in
important ways. First, the interaction of land cover and
the atmosphere causes a regulation of the hydrologic cycle
and energy budget, which makes it necessary for weather
and climate prediction. Land cover also plays a major role
in the carbon cycle by acting as a source and a sink of
carbon. Deforestation, aforestation, and re-growth cause
the release and sequestering of carbon, thereby affecting
atmospheric CO2 concentration and
the strength of the greenhouse effect (GCOS 2004, Masek
2001). Also, because regional climate conditions are a main
determinant of vegetation types, changes in vegetation and
land cover may indicate that climate change is occurring
(GCOS 2004). Finally, land cover is a useful indicator because
many climate-related variables that are difficult to measure
at the global level, such as surface roughness, can be inferred
in part from vegetation and land surface types; thus, land
cover can be used to infer other important climate variables
(GCOS 2003).

As a
subset of the land cover variable, monitoring of land cover
change is necessary for understanding the extent and severity
of anthropogenic and natural changes occurring. Land cover
changes may be grouped into one of two broad categories:
conversion or modification. Conversion refers to the change
from one cover type to another, such as conversion of forests
to pasture land. Modification refers to the maintenance
of the same cover type while changes to its attributes are
occurring. For instance, a forested area may be retained
as forest while major impacts to its structure or function,
such as those involving biomass or productivity, occur (LUCC
1997).

Land
cover products have historically been developed according
to specific project needs, with methods and results generally
not compatible across different land cover schemes. This
tendency has resulted in the development of remote sensing
datasets and methods that are difficult to compare, both
spatially and temporally. (Homer 2004) With regard to land
cover change, the monitoring process requires the existence
of (reasonably) reliable maps and datasets to construct
a time series for land cover over a particular area. Traditional
cartography provides some historical context, but because
many of these land cover products have not been properly
archived and transferred into electronic format, it is difficult
to construct an accurate time series.

Historic
background

Land
cover has been identified as a terrestrial essential climatic
variable in the original GCOS implementation plan and adequacy
reports.

Information
on the requirements and status of the land cover ECV which
have already been submitted to the UNFCCC is summarized
in the following
document73kb,
v01, 22 June 2007

ECV
land cover standards report

GTOS
is currently assessing the status of the development of
standards for each of the essential climate variables in
the terrestrial domain, as requested by UNFCCC SBSTA/COP
for its 23rd Session in Montreal, November 2005. The following
report, documentation and other resources have been compiled
for land cover. We welcome your comments and inputs in improving
and completing the analysis for biomass. Please send any
material and comments to the GTOS
Secretariat.

Listed
below are the major references that have been identified
in regards to methodology and standards for land cover.
Please inform us if you are aware of any other documentation
or material which could be considered.